/*3. Write the function: double max_norm(double *v, int n) to compute
the maximum norm of vector v[] with n elements. The max norm of a vector is
computed by taking the maximum absolute value of its elements.
In prob3() compute x1[]=a[][]*x0[], call max_norm() to compute the max_norm
x1[]. In order to normalize (or convert it to a unit vector), divide each
element of x1[] by the norm. Print the normalized x1[] using %12.4e. Then
copy x1[] as x0[] (to perform updating) and repeat the process nine more times. */